Embodiments described herein relate to a system and method for cleaning an exhaust gas recirculation (EGR) component. More specifically, embodiments described herein relate to a system and method for removing deposits in an EGR cooler.
Exhaust gas recirculation (EGR) is used to reduce nitrogen oxide (NOx) emissions in both gasoline and diesel engines. NOx is primarily formed when a mix of nitrogen and oxygen is subjected to high temperatures. EGR systems recirculate a portion of an engine's exhaust gas back to the engine cylinders. Intermixing fresh, incoming air with recirculated exhaust gas dilutes the mix, which lowers the flame temperature and reduces the amount of excess oxygen. The exhaust gas also increases the specific heat capacity of the mix, which lowers the peak combustion temperature. Since NOx is more readily formed at high temperatures, the EGR system limits the generation of NOx by keeping the temperatures low.
Many EGR systems include at least one EGR cooler connected in series or in parallel between an exhaust manifold and an intake manifold of an engine. Some engines, especially compression ignition or diesel engines, use the EGR coolers to cool the portion of exhaust gas being recirculated. The cooled exhaust gas has a lower latent heat content and can aid in lowering combustion temperatures even further. In general, engines using EGR to lower their NOx emissions can attain lower emissions by cooling the recirculated exhaust gas as much as possible.
Exhaust gas constituents in the exhaust gas being recirculated to the intake manifold may build-up on the EGR cooler. Further, various hydrocarbons may condense onto the EGR cooler. The build-up of deposits and condensation may cause a degradation of heat transfer efficiency and an increase in the pressure drop across the EGR cooler, which may eventually result in the overall loss of engine performance and efficiency.
The most common ways that deposit build-up are addressed include removing and cleaning the EGR cooler, and replacing the EGR cooler. Additionally, condensation of exhaust gas constituents has been addressed by delaying initiation of EGR under cold start conditions, limiting the amount of exhaust gas being recirculated, or limiting the amount of cooling applied to the recirculated exhaust gas in an effort to minimize the degree and amount of condensates. These measures, although effective in increasing the service life of engine components and decreasing the likelihood of failures, may be insufficient in addressing the impact that the EGR system has on the emissions generated by the engine.